1. Field of Invention
The present invention relates to a composition of an anti-glare coating, and more particularly to an anti-glare coating that comprises dispersant to prevent particles from aggregating.
2. Description of the Related Art
A transparent substrate such as a screen of a cathode ray tube (CRT), a panel or a touch panel of a liquid crystal display (LCD), a palm digital assistant (PDA), panes of glass for architectures, etc. has a layer of anti-glare (AG) film on a surface of the transparent substrate to decrease or eliminate reflections on the substrate to make viewing clearer and more comfortable.
A conventional composition of an anti-glare coating comprises resin, diluent and multiple particles. The particles include organic particles and inorganic particles. The organic particles may comprise polystyrene (PS), polymethyl methacrylate (PMMA), melamine formaldehyde resin, benzoguanamine, etc. The inorganic particles may include silica (silicon oxide, SiO2), aluminum oxide (Al2O3), calcium carbonate (CaCO3), etc. When the anti-glare coating is spread over a substrate and is cured, an anti-glare film is formed and the particles provide the anti-glare film to have a rough surface to decrease reflections of the substrate.
However, van der walls force forces the organic particles to aggregate and hydrogen bond will be generated between the inorganic particles to lead the inorganic particles to aggregate before the anti-glare coating is cured. Therefore, each particle-aggregation is large, so that a surface of the anti-glare film will become unevenly rough or even result in stuck pixel. Additionally, once the particles aggregate, they are hard to separate, so the particle-aggregations will precipitate in the anti-glare coating. Consequently, the anti-glare coating is hard to be coated uniformly over the substrate.
In U.S. Pat. No. 3,679,451, the anti-glare coating comprises a mixture of at least two dispersed incompatible polymers to make the anti-glare coating homogeneously. Thus, the anti-glare coating can be spread uniformly over a substrate. However, the incompatible polymers are unstable when they are mixed. Thus, the anti-glare coating with incompatible polymers is preferred to be produced by a batch process and not by a continuous procedure, wherein the batch process costs more than the continuous procedure.
In U.S. Pat. No. 4,582,761, an anti-glare coating comprises an aqueous dispersion of polyvinyl acetate (PVA) resin and aqueous dispersion of acrylic resin to provide an irregular surface of the anti-glare coating. However, polyvinyl acetate resin and acrylic resin have poor hardness. Therefore, the anti-glare coating with polyvinyl acetate resin and acrylic resin cannot be used for panels while current panels require high hardness.
U.S. Pat. No. 6,074,741 mention that a Japanese patent (No. 105738/1989) discloses an anti-glare coating that has ultra-violet curing resin and a silica pigment. However, silica particles are also prone to aggregate that leads to a poor anti-glare effect.
To overcome the shortcomings, the present invention provides a composition of an anti-glare coating to mitigate or obviate the aforementioned issues.